GREENE: That is sound from the starting line of the new Formula One race in Austin last fall. This summer, that same track was home to another race - which sounded like this...

(LAUGHTER)

GREENE: Those barely audible vrooms came from solar-powered race cars.

Terrence Henry of member station KUT went to find how far we have come in the race to create solar powered transportation.

TERRENCE HENRY, BYLINE: Anne Hildebrand straps on a helmet and gets ready to hop in her team's solar-powered race car. It's a low, sleek, flat vehicle covered in solar panels. Looks like something out of "The Jetsons." Seats just one. And goes a little slower than the Formula One cars, which go over 200 miles an hour.

ANNE HILDEBRAND: We've calculated that it could go I think 80, 88? But we can't actually do that because it's not legal on any roads.

(LAUGHTER)

HILDEBRAND: So, we're kinda bound by the speed limits.

(LAUGHTER)

HENRY: Hildebrand is an engineering student at Oregon State University. Her school and several others meet up once a year to race solar cars they built and designed themselves. It's called the Formula Sun Grand Prix.

But the race isn't about speed. It's an endurance race. In shifts, the drivers do laps all day and then charge in the hours before the sun goes down. Whichever car does the most laps in three days using nothing but the sun, wins.

HILDEBRAND: OK. Right here.

HENRY: This day is a sweltering Texas day, with plenty of sun. Hildebrand is eager for her turn to race. She'll be out on the track for the next four hours.

(SOUNDBITE OF HAMMERING)

HENRY: In the pit, there's plenty of clinking and clanking to get the car back on the track. Batteries have to be tested and wheels have to be fixed.

(SOUNDBITE OF TEAM FIXING BROKEN WHEEL)

HENRY: And elation, once Hildebrand's car is finally out of the pit.

(SOUNDBITE OF TEAM CHEERS)

HENRY: But it's not just car tinkerers who are turning to the sun for power. Last year, a solar-powered boat sailed all the way around the globe for the first time. A few weeks ago, a solar-powered plane completed a trip across the country.

ROGER DUNCAN: We're really not looking at solar as a mass transit option.

HENRY: Roger Duncan is a research associate at the University of Texas at Austin. He says right now, solar-powered cars, planes and boats are really only good for transporting a single passenger. That's because the bigger the vehicle, the heavier. It's difficult to move heavy weights using solar energy directly.

DUNCAN: However, we need to understand that solar power occurs in many different forms. In fact, the electric vehicles that are starting to be purchased around the county - and I own a plug-in hybrid vehicle - can indeed be powered by solar.

HENRY: He sees a future where there are solar panels everywhere - but they're feeding power into the electric grid, and then into lots of cars.

DUNCAN: You will see solar become ubiquitous. It's going to be on carports, and rooftops and walls and just about everywhere.

(SOUNDBITE OF HAMMERING)

HENRY: Back at the racetrack, the students' goal is to design cars that don't need charging stations or electrical outlets. And engineers here are willing to wait.

LOREN BROWN: Two years to build the car, and then we race it and fix things. Race it again.

HENRY: Loren Brown was on the winning team here at the Formula Sun Grand Prix. Oregon State won after going around the track 193 times. Since the race first began in 2000, the cars have been getting faster and lighter. Solar cars that used to have led acid batteries weighing over 300 pounds have been replaced by lithium batteries that weigh just a few dozen pounds.

BROWN: I don't know if we're doing anything new or groundbreaking, but I think we're learning a lot. That's why I'm here.